Wow! Just averaged 10 mpg on highway over 100 stretch at 65 mph in my 78 Jimmy. This can't be typical. I have a stock drivetrain with a stock 400 with a holley carb. I can't tell what kind of carb it is, looks new and does not have fuel bowls and is not efi (I wish). I love driving the Jimmy with the top down, but had to quit driving it because of the fuel consuption problem. I plan on installing a 383 from my chevelle soon, I averaged about 15 mpg in town in the chevelle. I don't want to waste my time with the swap if I can't get better fuel mileage than my approx. 7 mpg in town now,since I won't be able to afford the gas. My question is what is your typical fuel consumption in town or on the highway?